diabolical
adj. C1 Advanced US //ˌdaɪəˈbɑɫɪkəɫ// UK //dˌaɪəbˈɒlɪkəl// di·a·bol·i·cal
adj. extremely evil, cruel, or difficult. You use this to describe something that is so bad it feels like it was made by the devil.
adj. extremely wicked, cruel, or evil; also used to describe something exceptionally difficult or unpleasant. Often used in a hyperbolic sense to express strong disapproval.
The diabolical plan failed because of a small mistake.
The diabolical weather during the marathon made it impossible for the runners to finish the race.
The novel features a diabolical antagonist whose schemes are so intricate that they seem to have been designed by a master of chaos rather than a human mind.
From diabolic + -al.